Cushioning device for pneumatic hammers



Jan. 22, 1935. F. FAUDI CUSHIONING DEVICE FOR PNEUMATIC HAMMERS 2 Sheets-Sheet 1 Y Filed NOV. 29, 1932 Jan. 22, 1935. FAUDI 1,988,982

GUSHIONING DEVICE FOR PNEUMATIC HAMMERS Filed Nov. 29, 1952 2 sheets-sheet 2 1 5 1 Fig.1!) v Patented Jan. 22, 1935 UNITED STATES? CUSHIONING DEVICE FOR PNEUMATIC HAMMERS' many Application November 29, 1932, Serial No. 644,8 l9

In Germany December 18, 1931 I 1 Claim. (cuss-46) My patent .No. 1,924,234, dated August 29, 1933, describes'a method of cushioning the handle of a pneumatic hammer, in which the compressed air available from the compressed air mains or accumulators, for actuating the hammer mechanism, is also utilized for the damping or cushioning of the handle which is displaceably mounted in the hammer housing, and which parts, when the hammer is in operation, perform pulsating or jerky relative movements in rapid succession. The handle is attached, by means of a relatively thick piston rod, to a differential piston, which is adapted to slide in a chamber in the head of the hammer housing and which pis ton is loaded on both sides by the compressed air. The cushioning takes place in the space bounded by the piston surface remote from the piston rod and the handle, the end surface of the housing andthecylindrical inner surface of the chamber. The compressed, air which acts on the smaller piston surface'of the differential piston,,has a braking eflect in the opposite direction, that is to say serves for damping therelative backward movements of the moving parts. A channel or channels connect the main cushioning chamber with the damping chamber to permit the air to pass from one to the other to a certain extent during cushion oscillation.

According to the present invention the passages which determine the alterations in tension of the compressed air in previously determined graduation, or other connections controlling the throttling of the compressed air, instead of being out directly in the inner cylinder jacket which requires special and expensive apparatus and is diiiicult to carry out, are formed in a relatively thin walled interchangeable liner in which the differential piston slides. This liner is made separately, can easily be manipulated during operation and can be made in mass in any suitable way, to the accuracy necessary for its intended use. The same applies to the passages which formed in the liner. This important member, may be of any material suitable for its purpose in respect of hardness, resistance to wear and similar properties, that is to say independently and differing from the material of the head of the hammer, and specially constructed to withstand its special stresses.

In the forms of construction shown in the drawings Figure l is a longitudinal section through the head of the hammer.

Figure 1a illustrates one form of construction of-the' passages-which may be, for instance, four in number.

'Figure 2 is a cross section through the liner showing the passages. l

Figures 3 and 4 show the development of the liner.

Fig. 5 is a longitudinal section of the inner end' of-the piston and adjacent parts, of a modification. 5

Fig; 6 is a view showing half of the liner, partly in section, used in the modification of Fig. 5.

Figs. '7 and 8' show the development ofthe said liner. J i Figs. 9 and 10 show the development of a liner having passages-therein of 'different form. Figure 11 shows "a form of" construction in which the openings which provide the connection-between the compressed air piping and the head chamber, are located on the same transverse plane as the lower ends of the passages. The main hammer housing it contains the drivingmechanism and ends in the head chamber!) with the main cushioning chamber 0. "The partition d separates the latter from the interior of the hammer' h'ousing an The piston headf' of the differential piston f separates the main cushioning chamber from the damping chamber e. It carries, by means of the thick piston rod i the handle g.

In the head chamber enclosing the main cushioning chamber, the metal liner h is inserted. The piston head I is fitted in the inserted metal liner h, without any special packing members being provided, with its cylindrical surface fitting in good sliding fit in the liner, and is adapted to be displaced therein. The two controlling members, the piston valve formed by the piston head and the liner h which serves as the main cylinder, perform the relative sliding movements towards each other during the cushioning process while the hammer is in operation. The piston sweeps over the passages in the inserted liner h, for instance of the main slide valve, in one of the above described forms of construction, and determines the effective area of the passage or passages from the lower to the upper chamber, reducing or enlarging such passage or passages according to the direction of the stroke which it carries out in consequence of the pulsating movements of the hammer housing.

The inserted liner it extends to the base of the head chamber, and is held in position by the metal stufiing box rings 1" vand 2'", having inserted between them a deformable packing ring 2''. In order not to reduce, or as little as possible, the

constancy of the pressure of the braking air, it is advisable in the arrangement and formation of the passages determining the throttling and final separation of the compressed air, as described herein, not to havethe connection of the head chamber with the compressed air piping located in the middle of'the main cushioning'space 0' but to have it in the damping space, or in such manner that the supply piping is allowed to open into the main cushioning space at the end-of the passages so that the passages and the inlet from the supply piping are simultaneously closed,

The first mentioned case showninfFigure 1. The compressed air passes fromthe.compressed air piping it through the nozzle is and the passages k into the damping space e; the latter communicates through the passageswi th thelmain cushioning space 0. Therein the compressed air loads the larger piston surface of the piston head I, and

forces the piston f with the handle 9, in the position of rest and during. temporary interruptions in operation, always into the extreme position in which the differential piston and the handle is thrust out of the head of the chamber :asfar as permitted by the retaining devices 1'', i, i', which limits its displacement in this direction. Figures 2, 3 and 4 relate to Figure 1;

The passages .hfin liner it have control edges h" of similar form running helically on the'surface of liner. Certain passages which pass completely through the walls of the liner have, at their ends, bridges .h connecting and supporting the lateral edges of the liner.

The passages shown inFigurel have the same width as the pamages h of Figure 3. The right hand portion of the development shown in Figure 3 and the cross section according to Figure 2 indicate passages which merge at the upper end of the liner into two approximately semi-circular holeshifi- W In the modification-shown in Figures 5 to 8 the liner has eightpassagesofequal breadth but of different length. Their lower ends follow a helicalline;

In the embodiment illustrated in Figures 9 and the head chamber, are located on the same transverse plane as the lower ends of the passages h in the liner. The cross-sectional area of the open- 'ing k2 on the liner is added to the area of the throttled passages until, simultaneously with the latter, they are completely covered by the piston head,

,and the isolated quantity of compressed air, the

pressure of which is much increased by previous throttling, becomes a true air cushion for the piston. In the examples illustrated, this travel is of only short length, and this has been found to be "sufficient for the rare cases in which the oscillations extend to the maximum.

The breadth ofthe passages, their graduation according to length, the thickness of the walls of the liner, and the wall-bridges left in their upper ends, and also the pitch of the control edge are selected according to the needs of the particular case and according to the special requirements of the various fields of application.

:I claim:

Handle cushioning mechanism for pneumatic hammers comprising a cushioning cylinder having a compressed air "inlet, a cushioning piston reciproca-bly mounted in the cylinder, a piston rod connecting one side of the cushioning piston with the handle of the pneumatic hammer, and a liner secured in the cushioning cylinder and provided with at least one passage communicating with the compressed .air inlet and the space below the piston and adapted to -be covered by the piston before it reaches the end of a cushioning stroke to entrap a cushioning volume of compressed air under the piston, the passage or each passage having an oblique control edge cooperating with the lower edge of the piston.

. FRITZ FAUDI. 

